A fully deployed Terminal High Altitude Area Defence (THAAD) system at a golf course in South Korea

What is the THAAD missile system and how does it work?

The Terminal High Altitude Area Defence (THAAD) system is designed to intercept and destroy short and medium-range ballistic missiles during their “terminal” phase of flight when they are falling towards the target.

The $1billion system was developed by the Pentagon following the failure of Patriot air-defence missiles to shoot down Saddam Hussain’s Scud rockets in the first Gulf war.

THAAD missiles are 20ft long, weigh nearly a ton and fly at up to 6,300mph, more than eight times the speed of sound, up to an altitude of around 93 miles.

They do not carry an explosive charge because it could detonate the warhead of the target missile – which could contain a nuclear device.

Instead they rely on a “hit-to-kill” approach, using infrared sensors to track the incoming missile and ramming it head-on to destroy it.

Admiral Harry Harris, who heads the US Pacific Command, said THAAD will “be able to better defend South Korea against the growing North Korean threat”.

China “firmly opposes” the system’s arrival in the region, which it views as a threat to its own security.

This is because it could possibly shoot down its own nuclear missiles.

A typical THAAD battery includes at least six launcher vehicles, each capable of firing eight missiles.

A Terminal High Altitude Area Defence (THAAD) interceptor is launched during a successful intercept test

Why did the US test THAAD recently?

Incredible footage showed the US military shooting down a missile similar to the ones launched by North Korea.

US forces tested their Terminal High Altitude Area Defence (THAAD) system in Alaska at an incoming target over the Pacific Ocean.

The medium-range ballistic missile was detected, tracked and intercepted on July 31, military bosses have revealed.

The test was a show of force two days after Kim Jong-un launched his latest missile – and then bragged it could hit anywhere in America.

Kim has also threatened to “reduce South Korea to ashes” after Seoul’s joint missile defence drills with the US military.

It follows North Korea’s underground test of what it claims is a 120 kiloton hydrogen bomb. and the threat of further tests of the regime’s long-range missiles that could theoretically hit as far away as Chicago.